alleryStart learning →Where is angiotensin I converted into angiotensin II, and by which enzyme?
AIn the lungs, by angiotensin converting enzyme
BIn the kidneys, by the enzyme renin itself
CIn the liver, by hepatic angiotensinogenase
DIn the adrenal cortex, by aldosterone synthase
Answer & Solution
Correct answer: A. In the lungs, by angiotensin converting enzyme
1. Cells of the juxtaglomerular apparatus in the kidney answer falling blood flow by secreting renin.
2. Renin converts angiotensinogen, a plasma protein made by the liver, into angiotensin I.
3. Angiotensin I then circulates to the lungs, where angiotensin converting enzyme turns it into angiotensin II.
4. Angiotensin II is a powerful vasoconstrictor and also releases antidiuretic hormone and aldosterone.
5. Renin acts one step earlier, and the adrenal cortex supplies aldosterone rather than performing this conversion.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 20 "The Cardiovascular System: Blood Vessels and Circulation", section 20.4 Homeostatic Regulation of the Vascular System_
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